Powertrain system

Abstract

A powertrain system includes an internal combustion engine, a motor generator and a control device. The motor generator includes a rotating shaft connected to a crankshaft of the internal combustion engine via a torsional damper. The powertrain system is configured such that the crankshaft and the above-described rotating shaft are not connected to a drive shaft of a vehicle at least at the time of engine start. The control device is configured to execute a cranking torque amplification control that controls the motor generator such that the MG torque output from the motor generator for cranking the internal combustion engine fluctuates in a resonant period of the torsional damper while making a fluctuation center of the MG torque higher than zero.

What is claimed is: 
     
       1. A powertrain system, comprising:
 an internal combustion engine including a crankshaft; 
 a motor generator including a rotating shaft connected to the crankshaft via a torsional damper; and 
 a control device configured to control the internal combustion engine and the motor generator, wherein 
 the powertrain system is configured such that the crankshaft and the rotating shaft are not connected to a drive shaft of a vehicle equipped with the powertrain system at least at a time of engine start, 
 where a direction of an MG torque, which is a torque output from the motor generator when the crankshaft is rotated in a forward rotation direction, is positive, the control device is configured to execute a cranking torque amplification control that controls the motor generator such that the MG torque output from the motor generator for cranking the internal combustion engine fluctuates in a resonant period of the torsional damper while making a fluctuation center of the MG torque higher than zero. 
 
     
     
       2. The powertrain system according to  claim 1 , wherein
 in the cranking torque amplification control, the control device fluctuates the MG torque using a torque range on a positive side and a torque range on a negative side. 
 
     
     
       3. The powertrain system according to  claim 1 , wherein
 in the cranking torque amplification control, the control device fluctuates the MG torque in a sine wave shape. 
 
     
     
       4. The powertrain system according to  claim 1 , wherein
 in the cranking torque amplification control, the control device fluctuates the MG torque in a rectangular wave shape. 
 
     
     
       5. The powertrain system according to  claim 1 , wherein
 the control device is configured to execute the cranking torque amplification control when outside air temperature is lower than a first threshold value. 
 
     
     
       6. The powertrain system according to  claim 1 , wherein
 the control device is configured to execute the cranking torque amplification control when temperature of the internal combustion engine is lower than a second threshold value. 
 
     
     
       7. The powertrain system according to  claim 1 , wherein
 the control device is configured to execute the cranking torque amplification control when voltage of a battery that supplies electric power to the motor generator is lower than a third threshold value. 
 
     
     
       8. The powertrain system according to  claim 1 , wherein
 the control device is configured to execute the cranking torque amplification control when state of charge of a battery that supplies electric power to the motor generator is lower than a fourth threshold value. 
 
     
     
       9. The powertrain system according to  claim 1 , wherein
 the vehicle is a series hybrid vehicle or a range extended electric vehicle in which the internal combustion engine is dedicated to electric power generation and the motor generator generates electric power using a motive power of the internal combustion engine.